For 15 years, Navy Capt. Judith Epstein has toiled at the Naval Medical Research Center to develop a malaria vaccine. As a Harvard-trained pediatrician, she hoped to develop an immunization that would protect deploying troops and possibly prevent the deaths of 660,000 people each year, including one child every minute.

On Aug. 8, in an article published in the journal Science, the world learned that Epstein and her colleagues are closing in on that goal.

Epstein and other researchers from NMRC, the Walter Reed Army Institute of Research, the National Institutes of Health and Sanaria Inc. of Bethesda, Md., conducted a study in which they injected 40 subjects with a vaccine developed from a weakened strain of the deadliest form of malaria, Plasmodium vivax.

They then let malaria-ridden mosquitoes feast on human subjects and sat back and watched.

Malaria symptoms — high fever, sweats, chills and aches — take about 10 days to develop after a person is infected.

In this study, though, no one became ill. Not on Day 10, Day 11 or later.

By Day 14, Epstein felt she was witnessing history.

“I just had this feeling like, ‘Oh my God. They are not getting sick. I’m right in the middle of a scientific breakthrough,’ ” she said.

The Navy and Army have worked to develop malaria preventives and treatments for decades. In the 1970s, the Navy discovered the basic foundation for the current vaccine: By irradiating mosquitoes, scientists could weaken the Plasmodium vivax. When the weakened strain was transferred to patients, it gave them immunity.

But there were issues with the delivery system, according to Epstein.

“It wasn’t ideal. In order to get the protection, the patients had to get a thousand mosquito bites, about 200 each day for a series of days,” she said.

In 2002, her predecessor as director of the Navy’s malaria program, retired Navy Capt. Stephen Hoffman, founded Sanaria Inc., to develop and manufacture a vaccine that didn’t need mosquitoes to make it work.

NMRC worked with Hoffman to test that product in 2009 and 2010.

It yielded mixed results. Delivered the common way most vaccines are given, through an injection into the skin or under the skin, all but two of the 40 patients developed malaria.

On an airplane after that study, Epstein came up with the idea to deliver the PfSPZ vaccine intravenously — something that had been done before with monkeys.

“Mosquitoes bite you. They inject the parasite directly into the bloodstream. We had to give it IV,” she said.

It worked with stunning success: 100 percent protection.

The experiment was the first for the NIH’s National Institute of Allergy and Infectious Diseases’ Vaccine Research Center. NIH researchers are thrilled to fund and support the project.

“The global burden of malaria is extraordinary and unacceptable,” said Dr. Anthony Fauci, NIAID’s director. “Scientists and health care providers have made significant gains in characterizing, treating and preventing malaria; however, a vaccine has remained an elusive goal. We are encouraged by this important step forward.”

According to Fauci and Epstein, a commercial version of the vaccine is still at least four years off. More studies need to be done on larger groups and to address dosing and delivery issues.

Trials are scheduled by other investigators for Tanzania and Mali. Those trials will take the vaccine to the heart of the malaria epidemic.

Epstein, who celebrated her success with a much-needed vacation, said she’s excited about the future.

“This is a multiprong effort, but the Navy has been involved from the beginning ... it’s been the highlight of my career,” she said.